The 1500cc throttle and choke controls share the same basic design as the post-1970 1275cc arrangement, using the revised pedal, cable, and bell crank linkage system rather than the simpler direct cable-to-lever pull of the earlier 1275cc cars. The accelerator pedal connects to a cable that runs to a bracket on the inlet manifold, where a bell crank mechanism translates the cable pull into the correct lateral movement for the carburettor throttle spindles. The bell crank and link rod assembly is mounted on a bracket bolted to the inlet manifold, providing the necessary mechanical advantage and direction change for the twin SU HS4 carburettor geometry. Although the pedal, cable, and bell crank components are shared with the post-1970 1275cc, the carburettor return springs are specific to the 1500's HS4 carburettors and are not interchangeable with the 1275cc HS2 items.
1500cc Choke Cable
The choke cable on the 1500 connects to the carburettor jet linkage via a pin fitting. The cable routes from the dashboard through a grommet in the bulkhead, with a cleat secured to the heater case holding the cable in position and preventing it from chafing on surrounding components. Pulling the choke lowers the HS4 carburettor jets, enriching the fuel mixture for cold starting. A 1275cc choke cable from the earlier pre-1970 system must not be substituted, the cable length and routing are different.
Throttle Cable Adjustment
All throttle and choke cables, grommets, cleats, pedal bushes, return springs, bell crank assemblies, and link rods are available individually. When replacing a throttle cable, the free play at the carburettor end should be adjusted so that there is a small amount of slack with the pedal fully released, this ensures the butterflies close completely against their stop screws rather than being held slightly open by cable tension, which would cause a raised idle speed and potential difficulty bringing the engine back to a stable idle after acceleration.